V4 JIT: add hint for phi-node operands.

Not only is it preferable for the target of a phi-node to be stored in
the same location as one of the sources, but the same yields for the
sources. For example, in a loop, it is preferable to store the result
of a value used in a phi-node in the loop header to be stored in the
same location as that phi-node's target. Doing that will eliminate extra
moves that are generated to resolve differences between edges.

Change-Id: I0cb5fbe8915d602ac9b9a2a7e8b95cf47b1efb68
Reviewed-by: Lars Knoll <[email protected]>

1 files changed, 1 insertions, 0 deletions

diff --git a/src/qml/jit/qv4regalloc.cpp b/src/qml/jit/qv4regalloc.cpp
index 6a2f5ca640..2a3a1cd1bc 100644
--- a/src/qml/jit/qv4regalloc.cpp
+++ b/src/qml/jit/qv4regalloc.cpp
@@ -640,6 +640,7 @@ protected: // IRDecoder
             if (Temp *t = e->asTemp()) {
                 addUses(t, Use::CouldHaveRegister);
                 addHint(s->targetTemp, t);
+                addHint(t, s->targetTemp);
             }
         }
     }